Effects of electro-acupuncture on nerve growth factor and ovarian morphology in rats with experimentally induced polycystic ovaries

Despite extensive research on the pathogenesis of polycystic ovary syndrome (PCOS), there is still disagreement on the underlying mechanisms. The rat model for experimentally induced polycystic ovaries (PCO)-produced by a single injection of estradiol valerate-has similarities with human PCOS, and both are associated with hyperactivity in the sympathetic nervous system. Nerve growth factor (NGF) is known to serve as a neurotrophin for both the sympathetic and the sensory nervous systems and to enhance the activity of catecholaminergic and possibly other neuron types. Electro-acupuncture (EA) is known to reduce hyperactivity in the sympathetic nervous system. For these reasons, the model was used in the present study to investigate the effects of EA (12 treatments, approximately 25 min each, over 30 days) by analyzing NGF in the central nervous system and the endocrine organs, including the ovaries. The main findings in the present study were first, that significantly higher concentrations of NGF were found in the ovaries and the adrenal glands in the rats in the PCO model than in the control rats that were only injected with the vehicle (oil or NaCl). Second, that repeated EA treatments in PCO rats resulted in concentrations of NGF in the ovaries that were significantly lower than those in non-EA-treated PCO rats but were within a normal range that did not differ from those in the untreated oil and NaCl control groups. The results in the present study provide support for the theory that EA inhibits hyperactivity in the sympathetic nervous system.     

Steroid-induced polycystic ovaries in rats: effect of electro-acupuncture on concentrations of endothelin-1 and nerve growth factor (NGF), and expression of NGF mRNA in the ovaries,the adrenal glands,and the central nervous system

Previous studies on the effect of repeated electro-acupuncture (EA) treatments in rats with steriod-induced polycystic ovaries (PCO), EA has been shown to modulate nerve growth factor (NGF) concentration in the ovaries as well as corticotropin releasing factor (CRF) in the median eminence (ME). In the present study we tested the hypothesis that repeated EA treatments modulates sympathetic nerve activity in rats with PCO. This was done by analysing endothelin-1 (ET-1), a potent vasoconstrictor involved in ovarian functions, as well as NGF and NGF mRNA expression involved in the pathophysiological process underlying steroid-induced PCO.The main result in the present study was that concentrations of ET-1 in the ovaries were significantly lower in the PCO group receiving EA compared with the healthy control group (p < 0.05). In the hypothalamus, however, ET-1 concentrations were found to be significantly higher in the PCO group receiving EA than in the healthy control group (p < 0.05). Concentrations of ovarian NGF protein were significantly higher in the PCO control group compared with the healthy control group (p < 0.001), and these concentrations decreased significantly after repeated EA treatments compared with those in the PCO control group (p < 0.05) and were found to be the same as those in the healthy control group. In conclusion, these results indicate that EA modulates the neuroendocrinological state of the ovaries, most likely by modulating the sympathetic nerve activity in the ovaries, which may be a factor in the maintenance of steroid-induced PCO.     

Effect of electro-acupuncture on ovarian expression of α (1)- and β (2)-adrenoceptors,and p75 neurotrophin receptors in rats with steroid-induced polycystic ovaries

Background  

Estradiol valerate (EV)-induced polycystic ovaries (PCO) in rats is associated with an increase in ovarian sympathetic outflow. Low-frequency (2 Hz) electro-acupuncture (EA) has been shown to modulate sympathetic markers as well as ovarian blood flow as a reflex response via the ovarian sympathetic nerves, in rats with EV-induced PCO.     

Hypothalamic Neuroendocrine Functions in Rats with Dihydrotestosterone-Induced Polycystic Ovary Syndrome: Effects of Low-Frequency Electro-Acupuncture

Adult female rats continuously exposed to androgens from prepuberty have reproductive and metabolic features of polycystic ovary syndrome (PCOS). We investigated whether such exposure adversely affects estrous cyclicity and the expression and distribution of gonadotropin-releasing hormone (GnRH), GnRH receptors, and corticotrophin-releasing hormone (CRH) in the hypothalamus and whether the effects are mediated by the androgen receptor (AR). We also assessed the effect of low-frequency electro-acupuncture (EA) on those variables. At 21 days of age, rats were randomly divided into three groups (control, PCOS, and PCOS EA; n = 12/group) and implanted subcutaneously with 90-day continuous-release pellets containing vehicle or 5α-dihydrostestosterone (DHT). From age 70 days, PCOS EA rats received 2-Hz EA (evoking muscle twitches) five times/week for 4–5 weeks. Hypothalamic protein expression was measured by immunohistochemistry and western blot. DHT-treated rats were acyclic, but controls had regular estrous cycles. In PCOS rats, hypothalamic medial preoptic AR protein expression and the number of AR- and GnRH-immunoreactive cells were increased, but CRH was not affected; however, GnRH receptor expression was decreased in both the pituitary and hypothalamus. Low-frequency EA restored estrous cyclicity within 1 week and reduced the elevated hypothalamic GnRH and AR expression levels. EA did not affect GnRH receptor or CRH expression. Interestingly, nuclear AR co-localized with GnRH in the hypothalamus. Thus, rats with DHT-induced PCOS have disrupted estrous cyclicity and an increased number of hypothalamic cells expressing GnRH, most likely mediated by AR activation. Repeated low-frequency EA normalized estrous cyclicity and restored GnRH and AR protein expression. These results may help explain the beneficial neuroendocrine effects of low-frequency EA in women with PCOS.     

Effect of anti-NGF on ovarian expression of alpha1- and beta2-adrenoceptors, TrkA, p75NTR, and tyrosine hydroxylase in rats with steroid-induced polycystic ovaries

Estradiol valerate (EV)-induced polycystic ovaries (PCO) in rats are associated with higher ovarian release and content of norepinephrine, decreased beta2-adrenoceptors (ARs), and dysregulated expression of alpha1-AR subtypes, all preceded by an increase in the production of ovarian NGF. The aim of this study was to further elucidate the role of NGF in the ovaries by blocking the action of NGF during development of EV-induced PCO in rats. Control and EV-injected rats were treated with intraperitoneal injections of IgG (control and PCO groups) or with anti-NGF antibodies (anti-NGF and PCO anti-NGF groups) every third day for 5 wk starting from the day of PCO induction. Rat weight, estrous cyclicity, ovarian morphology, ovarian mRNA, and protein expression of alpha1-AR subtypes, beta2-AR, the NGF receptor tyrosine kinase A (TrkA), p75 neurotrophin receptor (p75NTR), and tyrosine hydroxylase (TH) were analyzed. Ovaries in both PCO and PCO anti-NGF groups decreased in size as well as in number and size of corpora lutea. mRNA expression of alpha1a-AR and TrkA in the ovaries was lower, whereas expression of alpha1b- and alpha1d-AR and TH was higher, in the PCO group than in controls. Protein quantities of alpha1-ARs, TrkA, p75NTR, and TH were higher in the PCO group compared with controls, whereas the protein content of beta2-AR was lower. Anti-NGF treatment in the PCO group restored all changes in mRNA and protein content, except that of alpha1b-AR and TrkA mRNAs, to control levels. The results indicate that the NGF/NGF receptor system plays a role in the pathogenesis of EV-induced PCO in rats.     

Pituitary gonadotropin-releasing hormone receptor content in rats with polycystic ovaries

A single injection of estradiol valerate (EV) induces, after a lag period of 4-6 wk, a chronic anovulatory polycystic ovarian (PCO) condition in adult rats. This condition is associated with a selective compromise of luteinizing hormone (LH) release and/or synthesis reflected in low basal serum LH concentrations, decreased pituitary content of LH, and decreased gonadotropin-releasing hormone (GnRH)-stimulated LH secretion. The present study was undertaken to determine to what extent the aberrant LH release in rats with PCO could be related to alterations in pituitary content of GnRH receptors. Pituitary GnRH-receptor content was assessed by the evaluation of saturation binding of a GnRH analog, [125I]-D-Ala6-des-Gly10-GnRH, to pituitary membrane preparations. The receptor content of pituitaries from rats with PCO was compared to that obtained from intact animals at estrus and diestrus. Receptor levels in ovariectomized normal rats and rats with PCO were also assessed. The pituitary GnRH receptor content in PCO rats was similar to that observed in normal controls at estrus and was significantly lower than that for rats at diestrus. Although a twofold increase in pituitary GnRH receptor content was observed at 28 days following the castration of control rats, GnRH receptor content in the pituitaries of PCO rats, at 28 days following ovariectomy, remained unchanged. Although, castration-induced elevations in mean serum LH and follicle-stimulating hormone (FSH) concentrations were observed in both the PCO and control animals, the rise in both gonadotropins was significantly attenuated in the PCO-castrates when compared to the ovariectomized controls. Since GnRH is a major factor in the regulation of pituitary GnRH receptor content, these findings suggest that hypothalamic GnRH release is impaired in rats with PCO and that this impairment is independent of any influences from the polycystic ovaries.     

Polycystic ovarian condition in estradiol valerate-treated rats: spontaneous changes in characteristic endocrine features

A chronic anovulatory polycystic ovarian (PCO) condition can be induced in rats with estradiol valerate (EV). We have previously shown that the early stages (8-10 wk after EV treatment) of the condition are characterized by low basal plasma luteinizing hormone (LH) and estradiol concentrations, as well as poor LH responsiveness to LH-releasing hormone (LHRH). These observations suggested that alterations in pituitary LH secretory activity may be involved in induction and maintenance of the PCO condition. In order to examine this possibility we have measured basal plasma LH and follicle-stimulating hormone (FSH) concentrations at various times (6, 15, 20 and 22 wk) after treatment with EV. AT 22 wk animals were subjected to a double LHRH pulse or equivalent treatment with saline. Basal plasma LH concentrations in EV-treated animals doubled between 6 and 22 wk. Despite this sharp increase, basal plasma LH concentrations at 22 wk were still significantly lower in EV-treated animals compared to proestrous controls. Basal FSH in EV-treated animals, remained in the proestrous range throughout the 22-wk period. Pituitary FSH and LH secretions in response to the LHRH challenge were significantly greater in EV-treated animals compared to proestrous controls. Plasma estradiol was significantly greater at 22 wk post-EV treatment than at 9 wk and this difference was reflected in the histology of the endometrium. These results indicate that a PCO condition is compatible with radical alterations in basal LH, and responsiveness to LHRH. Thus, aberrations in the ability to secrete LH do not appear to be causal in maintaining the condition.     

Effects of Electro-Acupuncture on Ovarian P450arom,P450c17α and mRNA Expression Induced by Letrozole in PCOS Rats

Hyperandrogenism is a core factor in the series of reproductive and endocrine metabolic disorders involved in polycystic ovary syndrome (PCOS). Abnormalities in enzymatic activity and the expression of ovarian granular cell layer P450arom and theca cell P450c17α can lead to an atypical environment of local ovarian hormones, including excessive androgen levels. Rat models prepared with letrozole exhibit similar endocrine and histological changes to those that occur in human PCOS. We used such a model to study the role of electro-acupuncture (EA) in regulating ovarian P450arom and P450c17α enzymatic activity and mRNA expression in PCOS rats. Female Sprague Dawley (SD) rats aged 42 days were randomly divided into 3 groups (control, PCOS, and PCOS EA) consisting of 10 rats each. The PCOS and PCOS EA groups were administered a gavage of 1.0 mg/kg⁻¹ of letrozole solution once daily for 21 consecutive days. Beginning in the ninth week, the PCOS EA group was administered low-frequency EA treatment daily for 14 consecutive days. After the treatment, we obtained the following results. The estrous cycles were restored in 8 of the 10 rats in the PCOS EA group, and their ovarian morphologies and ultrastructures normalized. The peripheral blood measurements (with ELISA) showed significantly decreased androgens (i.e., androstenedione and testosterone) with significantly increased estrogens (i.e., estrone, estradiol) and increased P450arom with decreased P450C17α. Immunohistochemistry and Western blotting methods showed enhanced expression of ovarian granular cell layer P450arom as well as decreased expression of theca cell layer P450C17α. Fluorescence quantitative PCR methods showed enhanced expression of ovarian granular cell layer P450arom mRNA as well as decreased expression of theca cell layer P450C17α mRNA. These results may help explain the effects of electro-acupuncture in changing the local ovarian hyperandrogenic environment and improving reproductive and endocrine metabolic disorders in PCOS.     

Development of the polycystic ovarian condition (PCO) in the estradiol valerate-treated rat

A wide range of experimental manipulations results in an anovulatory polycystic ovarian (PCO) condition in the rat. Although PCO has been studied in a number of these models, research has centered on the condition after it is well established rather than as it develops. Consequently, it is still not clear exactly what follicular cysts are or how and why they form. Therefore, we studied the development of PCO in rats treated with estradiol-valerate (EV). In this model, definitive cysts were present 8-9 wk after a single injection of EV. Animals were killed at 5, 11, 16, 21, 28 and 56 days after EV treatment. Serum was assayed for luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Ovaries were weighed and prepared for histologic examination. The ovaries were serially sectioned such that the number and size distribution of normal and atretic follicles could be assessed quantitatively. Oviducts were examined for the presence of ova. Immediately after EV treatment, ovulatory cycles ceased; by 16-20 days posttreatment, all animals exhibited persistent vaginal cornification. Basal concentrations of serum LH and FSH fell to a nadir at 11 days posttreatment, after which both gonadotropins exhibited a trend toward recovery. Within the first 28 days after treatment, ovarian weights declined significantly as did the total number of healthy follicles. Atretic follicles of all sizes were particularly numerous at 16 days. By 28 days, the decline in the number of healthy follicles reached a plateau. Numerous atretic, large secondary follicles were particularly prominent on the background of the decreasing number of normal follicles.(ABSTRACT TRUNCATED AT 250 WORDS)     

The physiological basis of complementary and alternative medicines for polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common endocrine disorder that is characterized by chronic hyperandrogenic anovulation leading to symptoms of hirsutism, acne, irregular menses, and infertility. Multiple metabolic and cardiovascular risk factors are associated with PCOS, including insulin resistance, obesity, type 2 diabetes, hypertension, inflammation, and subclinical atherosclerosis. However, current treatments for PCOS are only moderately effective at controlling symptoms and preventing complications. This article describes how the physiological effects of major complementary and alternative medicine (CAM) treatments could reduce the severity of PCOS and its complications. Acupuncture reduces hyperandrogenism and improves menstrual frequency in PCOS. Acupuncture's clinical effects are mediated via activation of somatic afferent nerves innervating the skin and muscle, which, via modulation of the activity in the somatic and autonomic nervous system, may modulate endocrine and metabolic functions in PCOS. Chinese herbal medicines and dietary supplements may also exert beneficial physiological effects in PCOS, but there is minimal evidence that these CAM treatments are safe and effective. Mindfulness has not been investigated in PCOS, but it has been shown to reduce psychological distress and exert positive effects on the central and autonomic nervous systems, hypothalamic-pituitary-adrenal axis, and immune system, leading to reductions in blood pressure, glucose, and inflammation. In conclusion, CAM treatments may have beneficial endocrine, cardiometabolic, and reproductive effects in PCOS. However, most studies of CAM treatments for PCOS are small, nonrandomized, or uncontrolled. Future well-designed studies are needed to further evaluate the safety, effectiveness, and mechanisms of CAM treatments for PCOS.     

Alterations in gonadotropin-releasing hormone-dependent gonadotropin secretion in rats with polycystic ovaries.

A single injection of estradiol valerate (EV) to adult female rats induces a persistent anovulatory polycystic ovarian (PCO) condition. During the 8-20-wk interval following EV treatment, this condition is associated with a selective compromise of LH release, decreased pituitary content of LH, and decreased GnRH-stimulated LH secretion. A marked increase in mean plasma concentrations of LH and enhanced LH response to GnRH occur after 20 wk post-EV treatment. Despite this apparent improvement, the PCO condition remains unchanged. The present study was undertaken to elucidate the underlying causes for these spontaneous improvements in LH parameters. We reasoned that these changes may be the result of alterations in 1) pituitary GnRH receptor levels; or 2) the mode of LH secretion, i.e. GnRH-dependent versus GnRH-independent; or 3) post-GnRH receptor events. Hence, we assessed pituitary GnRH receptor concentration as well as the pituitary content of LH and FSH in rats with PCO of 9 wk and 22 wk duration. To examine the possibility of a change in the mode of LH secretion, we examined the effects of in vivo suppression of LH secretion by treatment with a GnRH antagonist [N-Ac-D-Nal1, D-Phe2,3, D-Arg6, Phe7, D-Ala10]-GnRH (GnRH-ANTAG) in the same groups of animals. Mean pituitary weights were greater in the 9-wk-PCO than in the 22-wk-PCO animals. The pituitary concentration of GnRH receptors (on either a weight or milligram pituitary-membrane protein basis) was similar in the 9-wk- and 22-wk-PCO animals. Pituitary LH and FSH contents, however, were significantly higher (5-fold and 2-fold, respectively) in 22-wk-PCO rats compared to the 9-wk-PCO animals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Involvement of kisspeptin in androgen-induced hypothalamic endoplasmic reticulum stress and its rescuing effect in PCOS rats

Endoplasmic reticulum (ER) stress, with adaptive unfolded protein response (UPR), is a key link between obesity, insulin resistance and type 2 diabetes, all of which are often present in the most common endocrine-metabolic disorder in women of reproductive age, polycystic ovary syndrome (PCOS), which is characterized with hyperandrogenism. However, the link between excess androgen and endoplasmic reticulum (ER) stress/insulin resistance in patients with polycystic ovary syndrome (PCOS) is unknown. An unexpected role of kisspeptin was reported in the regulation of UPR pathways and its involvement in the androgen-induced ER stress in hypothalamic neuronal cells. To evaluate the relationship of kisspeptin and ER stress, we detected kisspeptin and other factors in blood plasm of PCOS patients, rat models and hypothalamic neuronal cells. We detected higher testosterone and lower kisspeptin levels in the plasma of PCOS than that in non-PCOS women. We established a PCOS rat model by dihydrotestosterone (DHT) chronic exposure, and observed significantly downregulated kisspeptin expression and activated UPR pathways in PCOS rat hypothalamus compared to that in controls. Inhibition or knockdown of kisspeptin completely mimicked the enhancing effect of DHT on UPR pathways in a hypothalamic neuronal cell line, GT1–7. Kp10, the most potent peptide of kisspeptin, effectively reversed or suppressed the activated UPR pathways induced by DHT or thapsigargin, an ER stress activator, in GT1–7 cells, as well as in the hypothalamus in PCOS rats. Similarly, kisspeptin attenuated thapsigargin-induced Ca²⁺ response and the DHT- induced insulin resistance in GT1–7 cells. Collectively, the present study has revealed an unexpected protective role of kisspeptin against ER stress and insulin resistance in the hypothalamus and has provided a new treatment strategy targeting hypothalamic ER stress and insulin resistance with kisspeptin as a potential therapeutic agent.     

Beta-endorphin concentrations in the hypothalamus, pituitary and plasma of streptozotocin-diabetic rats with and without insulin substitution therapy

The concentrations of beta-endorphin like immunoreactivity (beta-END) in the hypothalamus, pituitary and plasma were studied in rats of either sex, one month after induction of diabetes by single iv injection of streptozotocin. As controls, both normal and undernourished rats, weight-matched with diabetic rats, were used. Diabetic male and female rats had a marked depletion of beta-END stores in the hypothalamus and neurointermediate lobe (NIL) but not in the anterior pituitary. Depletion of beta-END was reversed to normal by insulin replacement therapy. Severe undernourishment was not as effective as diabetes to reduce beta-END stores in the hypothalamus and NIL. A significant reduction of beta-END was observed only in the NIL of undernourished female rats. Plasma beta-END and beta-lipotropin (beta-LPH) concentrations were not significantly altered in diabetic rats. These results indicate that the lack of insulin may affect beta-END synthesis in the hypothalamus and NIL.     

Prenatal ethanol exposure alters the expression of period genes governing the circadian function of beta-endorphin neurons in the hypothalamus

Sleep-wake disturbances and stress hyper-responsiveness have been observed in human neonates, children and adolescents who were exposed to alcohol during the prenatal period. Using the laboratory rat as an animal model, we investigated whether fetal ethanol exposure during gestational days 10-21 affects the circadian function of the stress-axis regulatory beta-endorphin neurons in the hypothalamus. Fetal ethanol-exposed rats showed abnormality in the circadian expression of proopiomelanocortin (POMC) mRNA encoding the peptide beta-endorphin in the arcuate nucleus of the hypothalamus during the adult period. These rats also showed altered circadian expression of the clock governing Period genes rPer1, rPer2 and rPer3, in the arcuate nucleus, and rPer1 and rPer 2 mRNA levels in the suprachiasmatic nucleus. Laser captured microdissection analysis identified constitutive expression of rPer1, rPer2 and rPer3 genes in beta-endorphin-containing neurons. These data suggest for the first time that fetal exposure to ethanol significantly alters the clock mechanisms governing the circadian function of beta-endorphin neurons.     

慢性炎症因子在多囊卵巢综合征中的作用机制

目的通过构建多囊卵巢综合征(PCOS)大鼠模型,探讨慢性炎症在PCOS发病过程中的作用机制。方法皮下埋置17-炔诺酮硅胶棒联合皮下注射HCG(Bogovich法)诱导PCOS大鼠模型。测定血清肿瘤坏死因子-α(TNF-α)、睾酮(T)空腹血糖(FPG)及空腹胰岛素(FIns)水平。结果模型组于6d形成PCO大鼠,24d构建PCOS大鼠模型成功。模型组血清TNF-α,T,FIns,FPG,胰岛素抵抗指数(Homa-IR)均高于对照组,胰岛素敏感指数(ISI)低于对照组。结论 Bogovich法诱导PCOS大鼠模型是研究PCOS发病机制的理想动物模型,慢性炎症可能诱导IR参与PCOS的发生与发展。     

Prevalence of ultrasonography proved polycystic ovaries in North Indian women with type 2 diabetes mellitus

Background  

Polycystic ovaries (PCO) and their clinical expression (the polycystic ovary syndrome [PCOS]) as well as type 2 diabetes mellitus (T2DM) are common medical conditions linked through insulin resistance. We studied the prevalence of PCO and PCOS in women with diet and/or oral hypoglycemic treated T2DM and non-diabetic control women.     

Effects of endogenous opioids on the development of reproductive function in rats]

The influence of opioid peptide on the process of formation of reproductive function in rats was studied. Administration of beta-endorphin to neonatal female rats did not affect the concentrations of oestrogen and androgen receptors in the hypothalamus and pituitary, whereas the content of testosterone receptors was significantly higher in both hypothalamus and pituitary. Chronic administration of beta-endorphin to both female and male rats does not affect the concentration of sex hormones. The results obtained indicate that chronic administration of beta-endorphin to neonatal female rats lead to formation of instable contacts in the mechanism of regulation of hypophysis gonadotropic function.     

Anti-Mullerian hormone levels reflect severity of PCOS but are negatively influenced by obesity: relationship with increased luteinizing hormone levels

The objective of the study was the comparison of anti-Müllerian hormone (AMH) levels among obese or overweight and normal-weight women with the four different polycystic ovary syndrome (PCOS) phenotypes and healthy control subjects. AMH levels were evaluated in four age- and body mass index (BMI)-matched groups of 25 normal-weight and 25 obese or overweight women each, belonging to the four main subsets of the syndrome resulting from combinations of the three diagnostic criteria [group 1: oligo- and/or anovulation (ANOV), hyperandrogenemia (HA), and polycystic ovaries (PCO) on ultrasonographic evaluation; group 2: ANOV and HA; group 3: HA and PCO, group 4: ANOV and PCO], and in 50 (25 obese or overweight and 25 normal weight) age- and BMI-matched healthy control subjects. Age, BMI, waist circumference, FSH, LH, prolactin, testosterone, Delta(4)-androstenedione, dehydroepiandrosterone-sulfate, 17alpha-OH-progesterone, fasting insulin, glucose, AMH, free androgen index, and homeostasis model assessment for insulin resistance index were analyzed. AMH levels were significantly higher in PCOS groups 1 and 2 compared with groups 3 and 4 and the control group and higher in PCOS groups 3 and 4 compared with the control group. AMH levels were significantly increased in normal-weight compared with obese and overweight women. AMH concentrations were independently predicted, in order of significance, by LH and testosterone levels, BMI (negatively), and the total number of follicles 2-9 mm in diameter. The differences in circulating AMH levels between the main phenotypic groups of PCOS women appear to reflect the severity of the syndrome, but are negatively affected by obesity. Increased LH levels might be the most significant independent link between PCOS-associated disorders of ovulation and the observed increase in circulating AMH concentration.     

Changes in beta-endorphin content in discrete areas of the hypothalamus throughout proestrus and diestrus of the rat

The aim of the present study is to investigate changes in beta-endorphin content in the hypothalamus during different stages of the estrous cycle. Groups of 9 to 10 Sprague-Dawley rats were sacrificed every two hours on proestrus from 8.00 to 18.00 h and groups of 7 to 8 rats were sacrificed on diestrus at 8.00, 12.00, 14.00 and 18.00 h. Preoptic suprachiasmatic region, posterior hypothalamus, arcuate nucleus and median eminence were dissected and assayed for beta-endorphin. A significant increase in beta-endorphin content was detected in the arcuate nucleus during proestrus (9.00 h: 1.76 +/- .31; 14.00 h: 4.10 +/- .85 microgram/g tissue wet weight). Levels did not change during diestrus (1.18 +/- .06 microgram/g). The increase caused significant differences in beta-endorphin values between both days at 12.00, 14.00 and 18.00 h, while the concentrations at 8.00 h were similar. The opposite pattern was observed in the median eminence with significantly higher proestrous beta-endorphin levels at 8.00 h (11.24 +/- 3.1 vs 3.52 +/- .64 microgram/g) and nonsignificant differences for the rest of the day. No significant change in beta-endorphin concentration was seen in the preoptic suprachiasmatic region over the day of proestrus (1.35 +/- .09 microgram/g). Diestrous beta-endorphin concentrations in this region were higher during the morning (2.60 +/- .65 microgram/g) and lower at 18.00 h (0.94 +/- .12 microgram/g) when compared to proestrous values. This pattern was caused by a 50% increase in beta-endorphin during the afternoon of diestrus. No changes were observed in the posterior hypothalamus on either day with comparable levels of beta-endorphin except at 18.00 h, when values were significantly higher on proestrus (1.66 +/- .30 vs 0.83 +/- .06 microgram/g).     

Pituitary and ovarian responses to luteinizing hormone releasing hormone in a rat with polycystic ovaries

Female rats injected with a single dose of 2 mg estradiol valerate (EV) develop anovulatory acyclicity characterized by persistent vaginal cornification and the formation of multiple large cystic follicles on the ovaries. In order to determine if these effects of EV are accompanied by changes in ovarian and/or pituitary function, the following studies were conducted. Ovarian androgen production was determined by the measurement at 4, 5 and 6 weeks after EV treatment of circulating dehydroepiandrosterone, androstenedione and testosterone. The capacity of the polycystic ovary to ovulate in response to luteinizing hormone releasing hormone (LHRH) stimulus was assessed. Ovarian histology was examined at the termination of the study (9 weeks after EV treatment). Pituitary function was assessed 9 weeks after the EV treatment by examining the acute changes in plasma luteinizing hormone (LH) concentration in response to a double pulse of LHRH. Plasma concentrations of the androgens were unchanged over the 3-week sampling period and were similar to those found in sesame-oil-treated normal cycling control rats. The ovaries from EV-treated animals were smaller than those of controls and the cystic follicles exhibited marked thecal hypertrophy and attenuation of the granulosa cell layer. The basal plasma LH concentration at 9 weeks after EV treatment were significantly lower than in proestrus controls and plasma concentrations of LH elicited by LHRH pulses was significantly lower than in controls. The relative increase in plasma LH following the LHRH stimulus was, however, greater in the EV-treated animals than in controls. In spite of the diminished LH surge elicited in response to LHRH, the EV-treated animals ovulated as indicated by the presence of fresh corpora lutea on the ovaries. These results indicate that androgens are not responsible for the polycystic ovarian condition in this system and that the polycystic ovary is capable of ovulatory function when appropriately stimulated.